Belt-tightener.



PATBNTED FEB. 20, 1906.

J. J. TEACHER. I BELT TIGHTENER. APPLICATION FILED JULY 3,1905.

3 SHEETS-SHEET 1.

' No. 812,899. PATBNTED FEB. 20, 1906.

' -J. J. TEACHER.

BELT TIGHTENER, APPLICATION FILED JULY 3,1905.

' 3 SHEETS8HEET 2.

\ IIIII/II/IIIIIIIIIIIII I if I jtuei'vdan- ITO-"812,899. PATENTED. FEB. 20, 1906.

' J. J. TEACHER.

BELT TIGHTENER.

APPLICATION IILHD JULY 3,1905.

3 SHEETS-SHEET 3.

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, UNITED STATES PATENT FFICE.

JOHN J. THACHER; CF ATTLEBORO, MASSACHUSETTS, ASSIGNOR TO BROWN AND SHARPE MANUFACTURING COMPANY, OF PROVI- DENCE, RHO E ISLAND, CoRPoRATIoN OF RHODE ISLAND.

BELT-Tl GHTEN ER."

Patented Feb. 20,1906.

Application filed July 8, 1905. Sei'ialNo- 268,029.

'- To all whom it may concern:

Be it known that 1, JOH J. THACHER, of Attleboro, in the county of Bristol and State of Massachusetts, have invented certain new and useful Im rovements in Belt-Tighteners and I do here declare the following speci fication, taken in connection with the accoman g drawin s, forming a art of the P y P same, to be a fu tion thereof. i,

The invention relates to devices for main ta'ining the tension of belts, and has for its object to provide a belt tightening or tensioning device which will maintain the belt at a uniform and constant tension during its operation. v

A further object is to provide a device of the'above character which will maintain a constant and uniform tension and at the same time will not interfere with the shifting or manipulation of the belt incident to its use in connection with pulleys of different size. These objects arefaccomplished by providing a belt-tightenin' or take-u device which is forced against t e belt by t e action of a fluid under pressure. The fluid under 1, clear, and exact descrippressure acts to force the belt-tightening device against the belt with a constant and uni form pressure, and this pressure is unaffected by variations in the position of the belttightening device due to any shifting or change in the relative ositionof the belt upon the pulleys over w 'ch it passes or due to a change in the relative position of such pulleys. 1

A further feature of the invention which ma be used with advantage in connection wit the feature already referred to consists in mainfaining the fluidressure for operating the belt-tightening evice by means of a pump, which is driven from the same source of power which drives the belt: and which ceases its action when the machine in whichthe belt and pum are embodied is thrown out of action. ith this construction the pressure applied to the belt tending to keep it under tension is uniformly maintained dur-.

ing .the o eration of thebelt and is relieved when the belt is out of operation, thus avoid. ing the strain and tension on the belt when it is idle. I a I For the purpose of illustratinga concrete application of my invention I have shown in the accompanying drawings the various features of the invention embodied in a grinding-machine. I

Thevarious features of the invention will be understood from the following detailed description of the mechanisms illustrated in the drawings and will be set forth in the claims.

In the drawings, Figure 1 is a transverse sectional elevation showing so much of a grinding-machine as 'is necessary to illustrate the application of the present invention thereto. Flg. 2 is a vertical sectional view on line 2 2, Fig. 1.

Fig. 3 is a detail eleva-.

tion showing the manner of mounting the f View showing-the arrangement of belts for driving the grinding-wheel and the pumping mechanism.

belt-tightening pulley, and Fig. 4 is a detail In the construction shown in the drawings The grinding-wheel of the machine is indi- I cated at W, and this wheel is mounted upon a cross-feed slide 9, which is in turn mounted upon a carriage 1 1. The cross-feed'slide 9is moved backward or forward upon the carriage 11 by suitable mechanism, (not shown,) an

the carriage 11 is recipro'cated ongsuitable guideways 12 and 13 by a mechanism which is not shown. The spindle on which the grinding-wheel W is mounted is provided with two pulleys 99 and 100 of different di ameters and the wheel is driven at one of two diflerentspeeds by means'of a drivingbelt 98, which passes over one of the pulleys shaft 6 and is driven by any suitable driving means.

The driving-belt 98 is maintained under tension by a belt-tightening or take-up mechanism embodying the features of my invention in the forms in which I prefer to em loy them. This mechanism comprises a elt- 95 and around a drum 101, which is secured to a tightening pulley 115, carried by arms 116 and arranged to enga e the belt 98. The

arms 11.6 are connecte' bya plate 117 and are pivoted 'uponstuds 11.8, arranged in line with each other and suitably secured in the" carriage 11. The ulley 115 is pressed continuously against t e belt 98 by theaction of a fluid under pressure contained in a cylinder 121 and acting upon a piston 120,-In'ounted in said cylinder. The piston 120 is connected with the belt-tightenin pulley 115 by means of a link 119, one en of which is pivoted' to the piston and the other end of which is pivoted to an arm 116*, extending upward from one of the arms 116, which carry the belt-engaging pulley. I By the action of the fluid under pressure. in the cylinder-121 the pulley 115 is forced against the belt 98 with a continuous and uniformpressure, while said pulley is free to move to accommodate any change in the position of thebelt incident to the backward or forward movement of the feed-slide 9 and is also free to move to take up or let out the belt when the belt is shifted from the ulley 99 to the pulley 100, or vice versa. T e movement oi the pliliflley-ll5 incident to such movements or s ting of the variation of the belt'does not result in an tension on the belt, since tl'le'fluid in the cylinder 121 is maintained at a constant pres"- sure and flows-into or out of the cylinder, as thecase may be, to accommodate the movements of the belt-enga 'ng ulley. I prefer to employ oi as t e fluid for maintaim-ng the pressure of the belt-engaging pulley, and the oil in the cylinder 121is mamtained at a constant pressure by a pump .124,

arr'angedwithin an oil tank 125 and connecte with thecylinder through pipes 121* and 126. The pipe 126 leads from the pump to a pressure-chamber 122,'and the pi e 121' leads from this res'sure-chamber to t e cylinder 121, bac

xpump duringl its operatioh acts to'continuously foice t e oil through the pipe 126-, and an excess of oil over and above that required to maintain the pressure upon the iston 120 escapes from the'pressure eham r 122 throu h a regulating-valve 127 which controls t ecommunication between the chamber 122 and a discharge-port 128. This regulatin -valve is held to its seat b a s ri 129,'the tinsion of which ma be ad jiust d l iy an adjusting sleeve 130. uri the operation of the pump a pressure be maintained in the pipes and in the cylinder 121 equal to the pressure required to compress the spring 129 and open the regulating-valve.- The pump 124 is driven continuously during the operation of the driving-belt 98 by means of a belt 131, passing over the drum 101, over guiding-pulleys 132, and over 'the drivingpull ey 133 for the pump mechanism. The

shaft.

of thepiston 120; The

pulley 133 is connected with the pump through a shaft 134 and bevel-gears 135, which connect the shaft 134 with the pump- With this construction the will act to maintain the pressure within the cylinder 1-21, and thus force the belt-engaging pulley against the belt with a uniform pressure during the time that the belt is in operation; but whenever the machine is stopped and the drum 101 ceases to revolve then the pum will cease to act and the ressure in the cy inder 121 will fall, thus re ievin the tension upon the belt.

hile I have shown and described my invention embodied in a grinding-machine, it will be understood that the various features of the invention may be used with advantage either separately or in connection with each other in other machines and in other relations where it is desirable to maintain a constant tension u on a belt. It will also be understood that th arrangement may be varied in embodying the features of invention in different constructions and adapting them for the most efficient operation under varyin conditions.

, Without attempting to set orth in detail pump ing a belt, a belt-engaging device, a piston connected with said device, devices for maintaming a fluid-pressure on said'piston, and driving mechanism for the belt and connec tion for driving the pressure maintaining dGVlOGSfIOIIl said driving mechanism, substantially as desci'ib'ed.

.2. A. b it tightening mechanism compris ing a belt, a belt-en 'ng device, a; piston. connected with said evice, and devices for maintaining a fluid-pressure on said piston driven from the; driving mechanism for the belt.

ing a belt-engaging evice, and means for forcing the device aglainst the belt by fluid under pressure, whi'c are renderedv inoperi ative upon the stopping of the belt.

' 4. A belt-tightening mechanism comprismg a belt-engaging device,-a piston connected with the device, and a pump for maintaining fluid-pressure on the piston and a common driv ng mechanism for the pump and belt. JOHN J. I Witnesses;

J. H. THURSTON, W. H. TnunsToN..

, a 5' 3'. A beltstlghtem mechanism compris-- 

